09-11-2020, 06:36 PM
On any other forum this would be considered a zombie thread, but since we're dealing with 80-year-old radios, no thread ever dies 
I ran into the same issue as islesailor, so I carefully dissected the 30-2488S cap to determine what was really inside. The description on the can is correct: there are three sections, but two of them (Red - 16uF and Green - 8uF) share a common negative lead (Black), and the third section (Blue - 12uF, Yellow - Neg.) is isolated, hence the 5 wires. There's no internal connection to the can.
Now for the schematic. I believe the wiring for the cap is incorrect as shown, for three reasons:
1. Since the black negative lead is common to the 16uF and 8uF, it can't possibly go to the two separate points shown.
2. The schematic doesn't match the way the 41-608 was wired at the factory.
3. The cap wiring doesn't match the power supply design of other, very similar sets, e.g., the 41-280, 41-250 and 41-610.
Unfortunately, the schematic error seems to be an old-timey literal copy/paste that got propagated through several models.
The factory wiring of the cap in the 41-608 does match the 41-280 design, and it makes sense. The negative side (black lead) of the 16uF and 8uF actually goes to chassis ground, which is typical of the design of many radios. I'd highly recommend wiring this way when re-capping, because wiring according to the 41-608 schematic could introduce noise on the output. I'll try to confirm this when I'm at that point in the restoration process.
Cheers!
-Brian
I ran into the same issue as islesailor, so I carefully dissected the 30-2488S cap to determine what was really inside. The description on the can is correct: there are three sections, but two of them (Red - 16uF and Green - 8uF) share a common negative lead (Black), and the third section (Blue - 12uF, Yellow - Neg.) is isolated, hence the 5 wires. There's no internal connection to the can.
Now for the schematic. I believe the wiring for the cap is incorrect as shown, for three reasons:
1. Since the black negative lead is common to the 16uF and 8uF, it can't possibly go to the two separate points shown.
2. The schematic doesn't match the way the 41-608 was wired at the factory.
3. The cap wiring doesn't match the power supply design of other, very similar sets, e.g., the 41-280, 41-250 and 41-610.
Unfortunately, the schematic error seems to be an old-timey literal copy/paste that got propagated through several models.
The factory wiring of the cap in the 41-608 does match the 41-280 design, and it makes sense. The negative side (black lead) of the 16uF and 8uF actually goes to chassis ground, which is typical of the design of many radios. I'd highly recommend wiring this way when re-capping, because wiring according to the 41-608 schematic could introduce noise on the output. I'll try to confirm this when I'm at that point in the restoration process.
Cheers!
-Brian
